1. Field of the Invention
This invention relates to a vertical type conveyor for carrying a load to be conveyed such as bulk cargo in the vertical direction or in inclined directions.
2. Description of the Prior Art
Conventionally, a vertical type conveyor, as disclosed in Japanese Patent Application Publication No. 61-3725, for example, is provided with a support, a plurality of pulleys rotatably supported by the support, a pair of conveyor belts traveling around the pulleys and a plurality of carrier rollers used for the conveyor belts. Both conveyor belts define an abutment area, in which both conveyor belts are in contact with and confront each other, and the carrier rollers are disposed at intervals in the abutment area in contact with both lug portions of each conveyor belt. Loads to be conveyed are pinched by both conveyor belts in the abutment area between both opposed lug portions to be moved along with the rotational drive of both conveyor belts.
According to the conventional vertical type conveyor as noted above, the carrier rollers are disposed so that first carrier rollers contacting a first conveyor belt are not opposed to second carrier rollers contacting a second conveyor belt with reference to each lug portion of the conveyor belts, and a force perpendicular to the belt surface is exerted against both conveyor belts. Accordingly, tension in the longitudinal direction of the conveyor belts is generated on both lug portions of the conveyor belts, and both conveyor belts are pinched with large force at the lug portions of the conveyor belts, so that the load to be conveyed is prevented from dropping out of a portion between both opposed lug portions.
However, a pinching force for pinching the load to be conveyed in the central portion of the conveyor belts is relatively lower. In order to avoid reduction of pinching force, it was indispensable to use a high rigidity conveyor belt whose pinching force is rather strong.
Further, since both conveyor belts are corrugated in shape as viewed from the side, the conveyor belts vary in peripheral speed at positions where respective carrier rollers are disposed, so that slip happens between the conveyor belts. As a result, the conventional vertical type conveyor generates slip between both conveyor belts and causes the conveyor belts to vibrate, thereby bringing about a large loss of drive force.